BACKGROUND OF THE INVENTION
The present invention relates to a method for securing covering materials onto a stent. The present invention also relates to a stent having a roughened or patterned surface. The present invention further relates to a device comprising a stent having a roughened or patterned surface and to a covering on the stent.
Stents are implanted within vessels in living beings in order to maintain patency of the vessels and to prevent collapse of the vessels. Stents also impede restenosis. Implantation of a stent is typically accomplished by mounting the stent onto an expandable portion of a balloon catheter, and maneuvering the catheter through the vasculature of the living being so as to position the stent at a desired location within a vessel lumen. Implantation also includes inflating the balloon to expand the stent so as to engage a wall of the lumen. The stent automatically locks into an expanded configuration allowing the balloon to be deflated and the catheter to be removed in order to complete the implantation procedure.
In some instances, it is desirable to provide localized pharmacological treatment of a vessel at the site supported by the stent. It has been found convenient to utilize the stent as a delivery vehicle for such purposes. However, because of the mechanical strength that is required to properly support vessel walls, stents are typically constructed of metallic materials which are not capable of releasing or carrying drugs. Various polymers are capable of carrying and releasing drugs but generally do not have the requisite mechanical strength. One solution to this problem has been a coating of a stent""s metallic structure with a polymer material in order to provide the stent with properties that permit the stent to support adequate mechanical loads and to deliver drugs.
Various approaches have been used to join polymers to metallic stents, including dipping, spraying and conforming processes. Such methods have failed to provide an economically viable method of applying a very even coating of polymer on the stent surfaces or to economically apply different thicknesses or different polymers in different areas on the same stent.
Some covers are not meant to be permanently adhered to the stent. These temporary covering materials are adhered to the stent by adhesives. A silicone based, two component adhesive has typically been applied to distal and proximal ends of the stents. One problem with the use of adhesive is a lack of compatibility. Adhesive residues on the stent inner surface are not biocompatible with the vessel wall and can, in some instances, cause inflammation of the vessel wall. One other problem with the use of adhesives is related to a non-uniform stent deployment at regions where the adhesive covers the stent. In some instances, the stent is not deployed in a fully lengthened position due to strong adhesive bonds between the adhesive and the stent.
U.S. Pat. No. 5,637,113, which issued Jun. 10, 1997, to Taraglia et al. describes a metallic stent which is wrapped with a polymeric film. The polymeric film is capable of carrying and releasing therapeutic agents. The polymeric film is secured to the metallic stent by a mechanism such as adhesive bonding. The adhesive is a copolymer of poly-L-lactic acid (L-PLA) and polycaprolactone (PCL). Other adhesives, heat bonding, solvent bonding and one or more mechanical fasteners, such as a metal clip are also suitable.
One product aspect of the present invention comprises a stent that comprises a structural support. The structural support comprises an outer surface that is roughened or patterned. The stent also comprises a polymeric film or sheet or tube that overlays the structural support. The polymeric sheet or film is retained to the structural support by the roughened or patterned outer surface.
Another embodiment of the present invention comprises a retaining system. The retaining system comprises a stent and a roughened or patterned surface on the stent.
One method aspect of the present invention is a method for adhering a polymeric sheet to a stent structural member. The method comprises providing a stent structural member with an outer surface. The method also comprises providing a polymeric sheet or tube. The method further comprises roughening or patterning the outer surface of the stent structural member and retaining the polymeric sheet or tube on the stent structural member at the roughened or patterned area.
Another embodiment of the present invention comprises a stent assembly. The stent assembly comprises a structural member with an outer surface that is roughened or texturized. The stent assembly also comprises a polymeric sleeve. The polymeric sleeve is retained to the structural member by the roughened or texturized surface.
One other embodiment of the present invention comprises a stent assembly. The stent assembly comprises a structural member with an outer surface that is roughened or textured. The stent assembly also comprises a polymeric sheet. The polymeric sheet is retained to the structural member by the roughened or textured surface.